1. Field of the invention
The present invention relates generally to a printed heater, and more particularly, to a printed heater having a heater base having a hole penetrating through the base.
2. Description of the related art
There have been known electronic copying machines and facsimile machines (hereinafter referred to as an "electrophotographic processing apparatuses") which are operated by an electrophotographic process.
During the electrophotographic process, toner is transferred onto a paper sheet to be transferred (hereinafter referred to as a "transfer paper sheet"). The toner transferred onto the transfer paper sheet is simultaneously heated to be fused and pressed thereagainst by a heater such as a heat roller so that the toner is fixed to the transfer paper sheet.
Recently, an electrophotographic processing apparatus which uses a different kind of heater than the heat roller is known.
The heater used in such an electrophotographic processing apparatus comprises an elongated substrate made of alumina ceramics or the like and a heating member formed into an elongated film by a well-known printing method. The heating member is made of a silver-palladium alloy and extends along the substrate. Both ends of the elongated heating member reaches to the respective ends of the substrate and therefore, the elongated heating member is formed into a belt-shape. Terminals, which are connected to a power source, are provided at the respective end portions of the heating member. The respective end portions of the heating member are covered by another film which is more electroconductive than the heating member in order to decrease the contact electric resistance between the terminals and the heating member. Since the heating member reaches momentarily about 200.degree. to 300.degree. C. and the instantaneous current through the heater is more than a few amperes the reliability of this contact is low as compared with the rest of the electrical circuits.
One way to increase the reliability of such an electric circuit is to increase the contact surface between the heating member and the terminal connecting to the contact surface. However, an increase of the contact surface usually causes an increase of the size of the heater and therefore is contrary to the recent demand for decreasing sizes. Any increase of the contact surface without an increase of the size of the heater may cause a short circuit somewhere.
Further, soldering or welding is commonly used for electrical connections. However, in case of connecting the terminals with the heater by soldering or welding, the films formed on the surface of the heater at both ends are likely to come off because the terminals are too large as compared with the thickness of the films. The films are too thin to be prevented from melting and coming off when large terminals are connected by soldering and welding. But since the heating member reaches momentarily at 200.degree. to 300.degree. C. and the instantaneous current through the heater is more than a few ampere which is 100 times as much as ordinary circuits, it is necessary to form the terminals into a large size. The reliability of these electrical connections is low as compared with ordinary electrical circuits.